Temperature sensors in thermometric devices, such as patient thermometers, have typically been ground to a certain component calibration which will affect the ultimate accuracy of the device. These components are then typically assembled into precision thermometer probe assemblies.
In past improvements, static temperature measurements or “offset type coefficients” have been stored into the thermometer's memory so that they can be either added or subtracted before a reading is displayed by a thermometry system, thereby increasing accuracy of the system. This is described, for example, in products such as those manufactured by Thermometrics and as described, for example, in U.S. Patent Publication No. 2003/0002562 to Yerlikaya et al.
A problem with the above approach is that most users of thermometry systems cannot wait the full amount of time for thermal equilibrium, which is typically where the offset parameters are taken.
Predictive thermometers look at a relatively small rise time (e.g., approximately 4 seconds) and thermal equilibrium is typically achieved in 2-3 minutes. A prediction of temperature, as opposed to an actual temperature reading, can be made based upon this data.
A fundamental problem with current thermometry systems is the lack of accounting for variations in probe construction/manufacturing that would affect the quality of the early rise time data. A number of manufacturing specific factors, for example, the mass of the ground thermistor, amounts of bonding adhesives/epoxy, thicknesses of the individual probe layers, etc. will significantly affect the rate of temperature change that is being sensed by the apparatus. To date, there has been no technique utilized in a predictive thermometer apparatus for normalizing these types of effects.
Another effect relating to certain forms of thermometers includes pre-heating the heating element of the thermometer probe prior to placement of the probe at the target site. Such thermometers, for example, as described in U.S. Pat. No. 6,000,846 to Gregory et al., the entire contents of which is herein incorporated by reference, allow faster readings to be made by permitting the heating element of a medical thermometer to be raised in proximity (within about 10 degrees or less) of the body site. The above manufacturing effects also affect the preheating and other characteristics on an individual probe basis. Therefore, another general need exists in the field to also normalize these effects for preheating purposes.